Method of continuous casting



Nov. 12, 1958 1.WOODBURN, JR 3,410,333

METHOD OF CONTINUOUS CASTING Filed Aug. lO, 1966 5 Sheets-Sheet l INVENTOR.

Nov. 12, 1968 J. WOODBURN, JR 3,410,333

METHOD OF CONTINUOUS CASTING Filed Aug. lO, 1966 5 Sheets-Sheet` I3 I Il H lill lll:

.Wil

Nov. l2, 1968 1. wooDBuRN, JR

METHOD CCNTINUOUS ASTING 5 Sheets-Sheet 5 lFiled Aug. l0, 1966 United States Patent 4 Claims. (Cl. 164-33) This application is a continuation-in-part of my copending application Ser. No. 327,641, tiled Dec. 3, 1963, now Patent No. 3,302,252.

The present invention relates to .a method of continuous casting.

A broad object of the invention is to attain advantages resulting from continuous casting, the method including continuously adding molten metal and continuously withdrawing the cast article at a corresponding rate, both of indenite duration within practical limits, with consequent economy in the molded product.

The invention relates more particularly to a method of casting wherein the cast product is formed in an upward movement through a mold and from which the molded product continues to move in an upward direction and is withdrawn in that direction from the mold.

A principal advantage of the invention is related to the rupward withdrawal of the molded product in that there is no necessity for providing means for preventing passage of extraneous molten metal through the mold, as would be the case where the molded product is withdrawn downwardly.

Another and more specific advantage of the invention is that due to the advantage just mentioned, the molded product may be solid or may be in hollow or tubular shape, such as pipe.

Still another object is to provide a method of continuous casting wherein novel means is provided for continuously adding molten metal to the :apparatus to enable indenitely continuous casting.

Other objects and advantages of the invention will appear from the following detailed description taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a vertical section-al view of one form of apparatus embodying the features of the invention;

FIGURE 2 is a vertical sectional view of another form of apparatus;

FIGURE 3 is a fragmentary sectional view of a portion of mold apparatus including means for oscillating the m-old, with the mold in retracted position;

FIGURE 4 isa view similar to FIGURE 3, but with the mold in advanced position;

FIGURE 5 is a detail sectional view of a starter section, located in the mold, utilized for starting withdrawal of the molded product;

FIGURE 6 is a diagrammatic view of a means for cutting the molded product in lengths;

FIGURE 7 is a diagrammatic view of another means for oscillating the mold; and

FIGURE 8 is a diagram-matic view of still another means for oscillating the mold.

Referring now in detail to the drawings, attention is directed lirst to FIGURE 1 showing one form of apparatus embodying the features of the invention. The apparatus includes a pouring tank 12 which may be of any suitable construction, defining a cavity 14 in which is disposed a ladle 16. The tank 12 may have an opening at any location such, for example, :as at the top in the present instance, and is provided with a flange 18 around the open top, for use in securing a cover 20. rl"he cover 20 may be secured in place by any suitable means such as clamps 22, there being a sealing gasket interposed between the cover Patented Nov. 12, 1968 and the ange 18 for sealing the interior of the tank against the escape of air which is introduced into the tank for pressure pouring.

Communicating with the interior of the tank is a suitable conduit 24 leading from a conventional pump or other air pressure developing apparatus indicated here diagrammatically which, upon controlled operation thereof, develops air pressure in the tank for pressure pouring of the molten metal.

The ladle 16 includes bounding elements composed of insulating refractory material 28, and embedded inthe upright wall elements thereof is `an induction coil 30 for connection with a suitable source of current (not shown) for induction heating the ladle and the molten met-al 32 therein, and maintaining it in molten form.

A pouring tube 34 leads from adjacent the bottom of the ladle, such as in or adjacent a cavity 36 in the bottom of the ladle, upwardly out of the ladle `and through the top cover 20 where it lcommunicates with the mold indicated generally at 38, which will be described in detail below herein. For convenience in supporting the pouring tube in position, the upper end thereof is provided with a flange 40 which engages and rests on the outer surface of the cover 20. A plate 42 is disposed on the cover 20 for supporting and adapting the mold 38, the plate having a recess for receiving the flan-ge 40 and the upper extremity of the tube 34 which projects above the flange. The mold 38 includes a central sleeve portion 44 provided with a central vertical bore 46 forming a cavity in which the molding of the product takes place. Preferably, the inner diameter of the pouring tube 34 is the same as the diameter of the cavity 46 to facilitate owing of the molten metal.

The sleeve 44 is of high heat conductivity as, for example, graphite or copper, for conducting the heat from the -molten metal therein for freezing it :and producing the molded product. The outer surface of the sleeve is preferably conical in shape tapering downwardly and supported in a cooling jacket 48 which may be of copper or other high heat conductive material. The cooling jacket 48 has an annular internal space 50 for circulation of a cooling liquid, such as water, for hastening the cooling action of the molten metal. Water is forced therethrough by suitable means indicated dia-grammatically at 52 which may withdraw water from a tap, and force it through an inlet conduit 56, :and after passing through the interior space 50, it passes through the outlet conduit 54 to waste. A suitable top plate 58 may be utilized for retaining the sleeve 44 in the cooling jacket.

The molten metal 32 is placed in the ladle 16 in any suitable manner, and then the ladle is placed in the tank 12 and the induction coil 30 connected with a suitable source of electrical supply. In the present instance, it is lowered through the open top of the tank, after which the cover 22 is secured in place, the mold 38 being carried by the cover or later applied thereto, as desired. After the ladle is thus introduced in the tank, air pressure is developed in the tank by the means 26, and due to the sealed condition of the tank the air pressure forces the molten metal 32 downwardly in the ladle and upwardly through the pouring tube 34, and thus into the Imold.

I have provided novel means for starting the molded product in the withdrawing action, namely a starter section `60, shown in detail in FIGURE 5. This starter section may be in the form of an inverted cup having an open lower end with .a plurality 'of cutouts or notches 62 in its lolwer marginal edge, and is provided with an extension '64 by which a line or cable 66 may be secured. It is lowered into the mold to a position indicated in FIGURE 5, in which its lower end is immersed in the molten metal, the level of the latter being indicated by the line 68. The starter section' 60 may be made of a metal having a melting point higher than that of the -metal being cast, eg.,

steel having a melting point of in the neighborhood of 500 F. higher than cast iron The cooling action on the molten metal in the mold will already have been started, and the metal being cast when it freezes will grip the starter section with sufiicient mechanical force to be Withdrawn by the starter section when the latter is raised. The cooling water passed through the cooling jacket continues the freezing operation, the outermost portion of the column of molten metal in the mold cavity being frozen first in an annular or pipe form. The starter section is then withdrawn by suitable hoist means (not shown) 'withdrawing the molten product or pipe.

After the molded product or pipe has been thus started, the withdrawing .action is continued with a plurality of extraction rollers frictionally engaging the pipe, which upon rotation thereof (by suitable means not shown) in the directions indicated, withdraw the molded product or pipe now identified at 72. It will be understood that the peripheral speed of the extraction rollers is such as to withdraw the molded product at the desired rate according to the desired rate of molding, taking into consideratio-n all other factors affecting the molding operation. The rate of l'Withdrawal of the molded product or pipe 72, together 'with the temperatures involved, determines the wall thick ness thereof, it being understood that a slower rate of withdrawal results in a thicker-walled pipe or a solid bar, other factors being equal. Similarly, a different temperature of molten metal will result in different wall thickness, other factors being equal, and the same is true with respect to the temperature of the cooling water in the cooling jacket `48 and the rate of flow thereof.

It is desired to cut the molded product in lengths and to do so without stopping or otherwise interfering with the constant withdrawal of the molded product. To accomplish this end, the cut-off device is arranged to move upwardly with and at the same rate as the molded product. Any of various arrangements may be utilized for this purpose, one being shown diagrammatically in FIG- URE 6, where a pulley 74 is driven at a peripheral speed equal to that of the extraction rollers 70. A cable 76 is trained over that pulley and over a series of other pulleys 78, the opposite ends of the cable being connected above and below respectively to a cutting means indicated generally at 80, including a cutting element 82 for cutting the product. Upon rotation of the pulley 74 in the appropriate direction, clockwise in the arrangement shown, the cutter means `80 is elevated with the product. The cutter element 82 during this operation is operated and moved against the product, cutting the latter. Suitable means may be employed for controllably operating the pulley 74, such as mounting it on a common shaft with one of the extraction rollers, and providing a clutch means for controllably elevating the cutter means. The cutter means may be lowered by any suitable means such as by gravity.

The embodiment illustrated in FIGURE 2 includes the principal features included in the apparatus of FIGURE 1, with additional features described below. The apparatus of FIGURE 2 includes the tank 12, ladle 16, pouring tube 34, and mold 38. Instead of the single inlet conduit 24, there is in addition an outlet conduit 84 for controlling the flow of compressed air in and out of the tank 12. Suitable pump means 86 is provided for pumping compressed air into the tank through the inlet conduit 24 and controllably removing it therefrom through the outlet conduit 84 for controllably varying the air pressure in the tank.

In .addition to the various structural elements incorporated in the apparatus of FIGURE 1, there is also a vertical filling tube 88 which extends through the cover 20 and terminates closely adjacent the bottom of the ladle, and has a filling hopper element at the top exteriorly of the tank.

In addition to the various structural elements incorporated in the apparatus of FIGURE l, there is also a vertical filling tube 88 which extends through the cover 20 `and terminates closely adjacent the bottom ofthe ladle,

and has a filling hopper element 90 at the top exteriorly of the tank. The filling tube is, of course, sealed in the cover 20 to prevent escape of air from the tank therepast. An induction coil 92 surrounds the upper exposed portion of the filling tube for heating and maintaining in the molten state the portion of the molten metal that extends up into the tube, as it does in the normal operation of the apparatus.

In the operation of the apparatus of FIGURE 2, the molten metal is poured into the filling tube 88 until the level in the ladle rises to the desired height, such as adjacent the top thereof. Then air pressure is developed in the tank, lwhich forces the molten metal up through the pouring tube 34 and into the mold 38, and the molding operation is performed and continued as described above ini connection with FIGURE 1. The molten Imetal also rises in the filling tube 838, due to the air pressure, to a level effectively equal to the level of the liquid portion of the molten metal in the mold, and as the molding or casting operation is continued, the withdrawal of the metal from the `mold is compensated by additional molten metal forced thereinto by the air pressure which is constantly increased to maintain the desired level of molten metal in the mold.

An advantage of the invention is that oscillation of the molten metal can be effected. This is done by varying the air pressure in the tank. For example, if the air pressure is increased to a predetermined value, it may raise the level of the metal in the mold to a height indicated by the line 68a, and upon release of that pressure to a second and lower predetermined value, the level of the molten metal descends to a position, for example, indicated by the line 68b. This lowering of the level is done relatively rapidly, causing .a washing effect of the molten metal in the center of the pipe against the inner surface thereof, producing a more refined and clean-cut inner surface of the pipe. It will be understood that the lower limit indicated by the line 68b would be above the lowermost lim-it of any freezing effect in the molded product.

The upper end of the filling tube 88 is at least as high as the upper extremity of the mold so as to prevent overd fiow of the molten metal through the filling tube in the normal operation of the apparatus. The arrangement enables continuous filling or replenishment of the apparatus; for example, given a constant air pressure in the tank, molten metal may be introduced into the lling tube and the level resulting therein forces the metal up into the mold, and at the same rate at which the metal is introduced in the filling operation.

The apparatus is also adapted for reciprocation of the mold relative to the other portions of the apparatus and relative to the rate of withdrawal of the pipe. FIGURES 3 and 4 show a fragmentary portion of the apparatus incorporating means for oscillating the mold. In these figures, the mold 38 is provided with a surrounding flange 94 or a plurality of extensions at its lower end and another flange 96 or extensions at its upper end. Tie bolts 98 interconnect these two fianges for forming a rigid assembly of the various components of the mold, and the lower fiange 94 provides means for securing the pouring tube 34 to the mold.

This rigid mold assembly is detachably supported on an extension 100 which is annular in form and mounted on the top 20 of the tank. This extension 100 receives the upper end portion of the pouring tube 34 for reciprocating movement therein, a suitable bushing 102 being secured as by welding to the pouring tube for sealing around it against the escape of the compressed air. The bushing 102 is secured to an outer bushing 103 and the two together `rise and fall with the pouring tube and mold assembly. The bushing 103 has bearing engagement with a surrounding wall element 105 included in the extension 100.

Power means, such as a plurality of hydraulic ram means 104, is provided for raising the mold. These ram means are mounted on the cover 20 and have pistons 106 engageable with the lower ange 94. Upon extension of the rams 106 through suitable power means (not shown) the ange 94 and thus the mold assembly is raised, carrying also the pouring tube 34 therewith.

The mold assembly is raised to its upper limit at a rate equal to that of the withdrawal of the molded pipe, and then abruptly lowered while the pipe continues to be withdrawn at its normal rate. This oscillating action frees the pipe from the mold, thus minimizing the static friction adherence of the pipe to the mold. This action results in greater average freeing action relative to a fixed mold and constant movement of the molded product or pipe.

It will be understood that the power ram means 104 is exemplary of various means that may be utilized for oscillating the mold. For example, as shown in FIGURE 7, cam means 108 may be provided for engaging a suitable element 110 of the mold 38, and upon rotation of the cam in the direction indicated, the mold will be raised. The cam is provided with a dr0p-0if surface 112 enabling an abrupt lowering of the mold, it being understood that the surface 112 may have a slight inclination to prevent an entirely free fall of the mold.

FIGURE 8 diagrammatically illustrates still another form of means for oscillating the mold. Instead of the cam 108, a saw tooth member 114 may -be utilized, each tooth 116 having a slope such that upon movement of the member 114 in the direction indicated and at a predetermined rate, the teeth will engage the element 110 and raise the mold at a rate equal to the withdrawal of the molded product or pipe, and upon the tooth passing beyond the element 110, the mold drops, as described in connection with FIGURE 7.

While I have herein shown certain preferred forms of the invention, it will be understood that changes may be made therein within the scope of the appended claims.

I claim:

1. A method of continuous casting in an arrangement wherein ia ladle of molten metal is sealingly enclosed in a tank, a mold having a continuous passage therethrough is positioned above the tank, and a pouring tube communi- Cates with the ladle adjacent the bottom thereof and rises through the tank for communication with the mold, comprising the steps of: applying superatrnospheric pressure in the tank to force the molten metal through the pouring tube and through the mold, freezing the molten metal in the mold and continuously withdrawing the frozen metal upwardly from the mold through the top of said passage, and intermittently replenishing the supply of molten metal in the ladle without interrupting the continuous casting operation.

2. The method of claim 1, and including the step of withdrawing the frozen metal at such a rate so as to form a tubular article.

3. The method of claim 1 in conjunction with the steps of raising the mold at a rate substantially equal to the rate of Withdrawal of the frozen metal, and lowering it abruptly.

4. The method of claim 1 in conjunction with the step of oscillating the molten metal and thereby raising and lowering the level thereof in the mold independently of and during the continuous withdrawal of the frozen metal.

References Cited UNITED STATES PATENTS 1,442,444 1/ 1923 Reeve 164-119 1,727,191 9/1929 Baily 164-283 2,135,183 11/1938 Junghans 164-83 2,660,769 12/1953 Bennett 164-337 X 2,799,065 7/ 1957 Whitaker 164-281 X 2,356,013 8/1944 Spooner 164-283 X FOREIGN PATENTS 927,172 5/ 1963 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner.

l R. S. ANNEAR, Assistant Examiner. 

1. A METHOD OF CONTINUOUS CASTING IN AN ARRANGEMENT WHEREIN A LADDLE OF MOLTEN METAL IS SEALINGLY ENCLOSED IN A TANK, A MOLD HAVING A CONTINUOUS PASSAGE THERETHROUGH IS POSITIONED ABOVE THE TANK, AND A POURING TUBE COMMUNICATES WITH THE LADLE ADJACENT THE BOTTOM THEREOF AND RISES THROUGH THE TANK OF COMMUNICATION WITH THE MOLD, COMPRISING THE STEPS OF: APPLYING SUPERATMOSPHERIC PRESSURE IN THE TANK TO FORCE THE MOLTEN METAL THROUGH THE POURING TUBE AND THROUGH THE MOLD, FREEZING THE MOLTEN METAL IN THE MOLD AND CONTINUOUSLY WITHDRAWING THE FROZEN METAL UPWARDLY FROM THE MOLD THROUGH THE TOP OF SAID PASSAGE, AND INTERMITTENTLY REPLENISHING THE SUPPLY OF MOLTEN METAL IN THE LADLE WITHOUT INTERRUPTING THE CONTINUOUS CASTING OPERATION. 